Structural members such as plates and beams can be made of two different materials of desirable properties that do not exist in any one material. For example, while ordinary steel has high strength and low cost, it is not highly corrosion resistant and it has a high density. Aluminum has high corrosion resistance and low density, but has less strength and a higher cost per unit weight than ordinary low cost steel. Stainless steel that includes nickel and chromium, has high strength and corrosion resistance, but has a high cost and a high density. A composite structure can be made by placing two sheets of different materials facewise adjacent and joining them, so that desirable properties of each material can be used. For example, a stainless sheet may form a corrosion resistant table top, while a steel sheet beneath it can provide strength at low cost.
Composite structures of different metals are not widely used because the cost for joining them is high. Known methods such as welding, riveting, screwing, brazing, etc. are often unsuitable, require the use of separate fasteners, and are relatively expensive. A method for joining sheet portions of dissimilar materials, which could be carried out at low cost, would facilitate the wider use of composite structures.